Recently, there have been many proposals to develop solar heating systems to replace, or at least compliment, conventional heating systems which rely generally on fossil fuels. However, the solar heating systems currently available are more complex and expensive than conventional heating systems. Many solar heating systems currently available must be integrated with conventional systems in order to provide adequate heat control. This usually requires relatively complex piping and controls in order to obtain maximum utilization of heat generated by the solar heating system with minimum reliance on the conventional system.
A primary problem with the current solar heating systems is that they are not packaged in a convenient form for use in conventional building structures or existing building structures, particularly in building walls. Most are roof-mounted units. Usually, they require a solar collector in communication via plumbing or ducting with some type of heat storage means which will store heat absorbed by the system during sunny periods and then release the heat at night or during cloudy days. The devices used for storage are generally heavy and take up a large volume because they store heat in, for example, water or rocks. Due to their great bulk such heat storage devices are usually placed in the basement of buildings or houses which results in high installation costs if the buildings or houses are already built. Even proposals for use of phase change materials provide for bulk remote location storage units in a basement or attic to which the solar heated fluid is piped. Furthermore, losses or inefficiencies result as the fluid travels between the solar collector and storage device.
Since presently available systems often require mechanical and electrical accessories such as valves, pumps, sensors and even small computers for efficient operation, installations with these devices can be expensive and have significant maintenance and reliability problems.
An additional problem with the currently available solar heating systems is that they tend to be architecturally incompatible with both existing buildings and existing building practices, particularly as self-contained wall and roof units. This incompatibility is both aesthetic and structural and is due in part to the design of the collectors which dictates that they are usually attached to the building structure as a type of auxiliary unit rather than being associated in an integral manner with the building structure. Even when integrated into the structure, they usually form part of the roof.
U.S. Pat. Nos. 4,003,367 and 4,055,055 illustrate the application of thermosiphonic principles to the making of a water heater and a boiler based on the collection of solar energy. However, neither of these disclosures are adapted for use as self-contained units and appear limited to the specific application as water heating devices.
U.S. Pat. No. 4,073,284 illustrates the use of a crystalline phase change material in a solar heating device operated by the saturated vapor of a heat carrier which is used to exchange heat with a phase change material having a storage mass capable of absorbing heat energy in the form of latent heat at a temperature just above room temperature. However, the principle of operation relies on the vaporization of a condensate, the pressure of which is regulated by a ducting system which is in communication with a bellows associated with the unit in order to control condensate level. This unit is designed to operate horizontally at ceiling level where heat is not efficiently distributed. In view of the necessity of operating against gravity between a liquid and condensate phases in the heat collection system, the unit appears inherently unsuitable for wall or steep roof locations.
U.S. Pat. No. 4,062,351 discloses a water collection trough panel having inlet and outlet ports connected to a piping system and presumably thence to a storage facility. In one embodiment disclosed in U.S. Pat. No. 4,062,351 (FIG. 19) it is stated that a thermosiphoning process can take place if the unit is tilted up and further it states that a supplemental use of heat retaining crystals can surround the heat transfer pipe in a unit employing fins to assist in exchange of heat from the panel to the material flowing in the transport pipe which presumably leads to a larger heat storage facility. However, the nature of the crystalline material referred to is not disclosed. It is not believed that this panel would be suitable for wall installation in view of the physical arrangements and the employment of the associated piping to take energy away from the panel rather than utilize it in situ. Thus, the unit is not self-contained.
Thus, the prior art as above exemplified fails to solve the basic problem of providing a self-contained unit requiring no external piping and which is architecturally and structurally compatible with both existing conventional buildings in new construction and as an addition thereto in older structures.